how to reference a specific worksheet on vba code

hi all,

I have a problem with regards to worksheet referencing. I have a workbook with 3 sheets. Sheet 1 and 2 contain the data while sheet 3 contains the command button that calls a userform.
in sheet 3 there are the active & vacant button for sheet 1 and 2 that when clicked will call a userform. in the userform there is a combobox that will contain the value based on sheet 1 and 2. if the sheet1 active button is clicked the userform combobox will display the active channels based on sheet1, same with sheet 1 vacant channel.. sheet2 vacant and active button will do the same from sheet 2.

My problem is i cannot reference the commandbutton code to the right sheet. it only works when the active/vacant commanduttons is located in sheet 1 and sheet2 but when they are located in sheet 3 and sheet 1 and 2 are hidden, it does not work.

I attached a copy of my workbook for your reference.

Regards,
rydysh

i tried this one but it didnt work, something is wrong with my referencing..

Private Sub UserForm_Initialize()
Dim r As Long
Dim ws As Worksheet
Set ws = Worksheets("sheet1")
With ws
For r = 2 To Range("C" & Rows.Count).End(xlUp).Row
If Range("D" & r).Value = "ACTIVE" Then
ComboBox1.AddItem Range("C" & r).Value
End If
Next r
End With
End Sub

One possibility.

thanks bakerman..it works